The invention relates to a valve arrangement for controlling and shutting off a fluid flow, in particular for a power plant.
In a multiplicity of technical applications in which fluid flows have to be controlled, valve arrangements of the type mentioned at the beginning are used, these valve arrangements having a control valve and a shut-off valve, the shut-off valve and the control valve being designed to be separate for safety reasons. During normal operation in the respective application, the control valve serves to control or regulate the volumetric flow and/or the pressure of the respective fluid flow. In contrast, the shut-off valve serves to shut off the fluid flow in an emergency. Such a shut-off valve is normally designed as an emergency-trip valve in order to be able to stop the fluid flow in as short a time as possible in an emergency. In certain applications, operating states may occur in which an additional fluid flow is required, and this additional fluid flow has to be controlled in addition to or alternatively to the main fluid flow controlled with the control valve. This additional fluid flow often has to be introduced at a different location from the main fluid flow. For example, the valve arrangement serves to control a steam flow which is fed to a steam turbine in a power plant. During normal operation, the control valve controls or regulates the steam feed to the high-pressure side of the steam turbine. For certain operating states, e.g. for a brief increase in power of the steam turbine, it is necessary to introduce additional steam at an intermediate stage of the steam turbine. This may be achieved with an additional steam line. In this case, it is expedient, in an emergency, to be able to shut off this additional steam line with the shut-off valve of the valve arrangement together with a main steam line controlled by the control valve. In order to achieve this, considerable outlay is required in order to connect the additional steam line to the valve arrangement.
The invention is intended to provide a remedy here. The invention as defined in the claims deals with the problem of specifying an improved embodiment for a valve arrangement of the type mentioned at the beginning, this improved embodiment simplifying, in particular, the coupling of an additional fluid flow to the shut-off valve.
This problem is solved by the subject matter of the independent claim. Advantageous embodiments are the subject matter of the dependent claims.
The present invention is based on the general idea of providing the valve arrangement with a bypass valve in addition to the control valve and the shut-off valve, all three valves being accommodated in a common housing. In this case, the bypass valve serves to control an (additional) fluid flow through a bypass which branches off in the housing upstream of the control valve and downstream of the shut-off valve. Since the shut-off valve is therefore located upstream of the other two valves, the shut-off valve, in an emergency, can shut off both the fluid flow controlled with the control valve and the fluid flow controlled with the bypass valve. The installation cost required to realize the bypass flow is reduced by the bypass valve being integrated in the common housing. Furthermore, the amount of material and space required for the entire arrangement is reduced. In particular in the case of a valve arrangement provided for a power plant, in which valve arrangement very large volumetric gas flows have to be controlled, the compact type of construction of the valve arrangement proposed has an especially advantageous effect.